This invention relates generally to a tone hole covering for wind instruments having a novel backing disk with an outer collar capable of flexing to relieve tension and resultant damage caused by repeated contacts with the tone hole. Preferred embodiments additionally provide improved support for the retainer that holds the pad assembly within the pad cup. Although generally applicable to all wood-wind instruments, embodiments of the present invention are especially suited for use in flutes.
During this century, instrument tone hole coverings, also called pad assemblies or simply pads, have typically comprised a cardboard backed wool felt disk covered with Goldbeater's skin, wrapped around the cardboard and glued to its backside. The pad is fixed in a pad cup mounted over an instrument tone hole on a hinged mechanism so that the tone hole is sealed when the pad is in its closed position. Although such pads can initially be made to seal well, sensitivity to its environment and lack of dimensional stability of the felt and skin causes the pad surface to lose its integrity and allow air to leak at the interface between the pad and the tone hole.
In 1987, in U.S. Pat. No. 4,704,939, a new pad was disclosed that can maintain a flat sealing surface regardless of variations in temperature, moisture, or altitude. As a result of this design, pad life is extended and closure of the tone hole consistently requires only a light touch by the musician. To accomplish these advantages, the improved pad has a semi-rigid supporting unit for the felt. The pad's design allows its surface to be tilted to fit a tone hole with a perfectly planar surface through the leveling process of triangulation or, by a wedging action, to distort the planar surface to perfectly match a damaged or imperfect tone hole.
One embodiment of the improved pads is constructed by stretching a skin across a cushion ring fitted within a recess formed between inner and outer collars on the lower radial face of a rigid backing disk having a bendable lower margin. The skin is folded around the edge of the backing disk and secured to the disk's back side. The pad is secured to its cup with a retainer comprising a washer and screw combination attached to a pad nut which is in turn attached to the bottom of the pad cup and centrally located within the cup's cavity. Upon tightening the retaining screw of the assembled unit, the flat washer forces the skin against the rigid inner collar. Other methods are also known for securing the pad assembly within the pad cup, including the usual friction held retainer utilized in French or open-hole pads.
Further improvements in pad design and methods of seating pad assemblies have been made which utilize a flexible stabilizing disk locked in an adjusted position with an adjusting agent, usually an adhesive, to support a flexible backing disk having inner and outer collars. As before, a cushion layer of uniform thickness is positioned between the inner and outer collars and the pad's sealing surface covered with a skin. Should the pad need further adjustment, the pad's surface can be made to coincide with the tone hole's surface by the usual wedging action of partial shims placed between the stabilizing and backing disks.
Although pads manufactured according to these improved designs have performed well, tears in the pad's skin covering can eventually occur on the portion of the skin that covers the semi-rigid backing disk's inner and outer collars. Replacement of pad assembly requires the installation of a new pad assembly and adjustment to conform the pad's surface to the tone hole surface and is both time consuming and expensive.
The tears are generally caused by the pad's inability to maintain an even tension on its skin during repeated contacts with the tone hole surface and during repeated expansion and contraction cycles experienced by the pad's skin caused by fluctuations in its moisture content. A backing disk and pad assembly are needed having components that can provide necessary support for the pad's sealing surface, maintain an even tension on the pad's skin and avoid tears resulting from fluctuations in moisture and repeated contacts with the tone hole surface in order to avoid the time consuming and expensive replacement of the failed pad assembly.